c语言字符函数

函数名: stpcpy

功  能: 拷贝一个字符串到另一个

用  法: char *stpcpy(char *destin, char *source);

程序例:

#include <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char string[10]; 
   char *str1 = "abcdefghi"; 
   stpcpy(string, str1); 
   printf("%sn", string); 
   return 0; 
} 

函数名: strcat

功  能: 字符串拼接函数

用  法: char *strcat(char *destin, char *source);

程序例: 

#include <string.h> 
#include <stdio.h> 
int main(void) 
{ 
   char destination[25]; 
   char *blank = " ", *c = "C++", *Borland = "Borland"; 
   strcpy(destination, Borland); 
   strcat(destination, blank); 
   strcat(destination, c); 
   printf("%sn", destination); 
   return 0; 
} 

函数名: strchr

功  能: 在一个串中查找给定字符的第一个匹配之处

用  法: char *strchr(char *str, char c);

程序例:

#include <string.h> 
#include <stdio.h> 
int main(void) 
 { 
    char string[15]; 
    char *ptr, c = 'r'; 
    strcpy(string, "This is a string"); 
    ptr = strchr(string, c); 
    if (ptr) 
       printf("The character %c is at position: %dn", c, ptr-string); 
    else 
       printf("The character was not foundn"); 
    return 0; 
 } 

函数名: strcmp

功  能: 串比较

用  法: int strcmp(char *str1, char *str2);

看Asic码，str1>str2，返回值 > 0；两串相等，返回0

程序例: 

#include <string.h> 
#include <stdio.h> 
int main(void) 
 { 
    char *buf1 = "aaa", *buf2 = "bbb", *buf3 = "ccc"; 
    int ptr; 
    ptr = strcmp(buf2, buf1); 
    if (ptr > 0) 
       printf("buffer 2 is greater than buffer 1n"); 
    else 
       printf("buffer 2 is less than buffer 1n"); 
    ptr = strcmp(buf2, buf3); 
    if (ptr > 0) 
       printf("buffer 2 is greater than buffer 3n"); 
    else 
       printf("buffer 2 is less than buffer 3n"); 
    return 0; 
 } 
  

  

函数名: strncmpi

功  能: 将一个串中的一部分与另一个串比较, 不管大小写

用  法: int strncmpi(char *str1, char *str2, unsigned maxlen);

程序例: 

#include <string.h> 
#include <stdio.h> 
int main(void) 
{ 
   char *buf1 = "BBB", *buf2 = "bbb"; 
   int ptr; 
   ptr = strcmpi(buf2, buf1); 
   if (ptr > 0) 
      printf("buffer 2 is greater than buffer 1n"); 
   if (ptr < 0) 
      printf("buffer 2 is less than buffer 1n"); 
   if (ptr == 0) 
      printf("buffer 2 equals buffer 1n"); 
   return 0; 
} 

函数名: strcpy

功  能: 串拷贝

用  法: char *strcpy(char *str1, char *str2);

程序例: 

#include <stdio.h> 
#include <string.h> 
int main(void) 
 { 
    char string[10]; 
    char *str1 = "abcdefghi"; 
    strcpy(string, str1); 
    printf("%sn", string); 
    return 0; 
 } 

函数名: strcspn

功  能: 在串中查找第一个给定字符集内容的段

用  法: int strcspn(char *str1, char *str2);

程序例: 

#include <stdio.h> 
#include <string.h> 
#include <alloc.h> 
int main(void) 
 { 
    char *string1 = "1234567890"; 
    char *string2 = "747DC8"; 
    int length; 
    length = strcspn(string1, string2); 
    printf("Character where strings intersect is at position %dn", length); 
    return 0; 
 } 

函数名: strdup

功  能: 将串拷贝到新建的位置处

用  法: char *strdup(char *str);

程序例: 

#include <stdio.h> 
#include <string.h> 
#include <alloc.h> 
int main(void) 
 { 
    char *dup_str, *string = "abcde"; 
    dup_str = strdup(string); 
    printf("%sn", dup_str); 
    free(dup_str); 
    return 0; 
 } 

函数名: stricmp

功  能: 以大小写不敏感方式比较两个串

用  法: int stricmp(char *str1, char *str2);

程序例: 

#include <string.h> 
#include <stdio.h> 
int main(void) 
{ 
   char *buf1 = "BBB", *buf2 = "bbb"; 
   int ptr; 
   ptr = stricmp(buf2, buf1); 
   if (ptr > 0) 
      printf("buffer 2 is greater than buffer 1n"); 
   if (ptr < 0) 
      printf("buffer 2 is less than buffer 1n"); 
   if (ptr == 0) 
      printf("buffer 2 equals buffer 1n"); 
   return 0; 
} 

函数名: strerror

功  能: 返回指向错误信息字符串的指针

用  法: char *strerror(int errnum);

程序例:

#include <stdio.h> 
#include <errno.h> 
int main(void) 
{ 
   char *buffer; 
   buffer = strerror(errno); 
   printf("Error: %sn", buffer); 
   return 0; 
} 

函数名: strcmpi

功  能: 将一个串与另一个比较, 不管大小写

用  法: int strcmpi(char *str1, char *str2);

程序例:

#include <string.h> 
#include <stdio.h> 
int main(void) 
{ 
   char *buf1 = "BBB", *buf2 = "bbb"; 
   int ptr; 
   ptr = strcmpi(buf2, buf1); 
   if (ptr > 0) 
      printf("buffer 2 is greater than buffer 1n"); 
   if (ptr < 0) 
      printf("buffer 2 is less than buffer 1n"); 
   if (ptr == 0) 
      printf("buffer 2 equals buffer 1n"); 
   return 0; 
} 

  

函数名: strncmp

功  能: 串比较

用  法: int strncmp(char *str1, char *str2, int maxlen);

程序例: 

#include <string.h> 
#include <stdio.h> 
int  main(void) 
{ 
   char *buf1 = "aaabbb", *buf2 = "bbbccc", *buf3 = "ccc"; 
   int ptr; 
   ptr = strncmp(buf2,buf1,3); 
   if (ptr > 0) 
      printf("buffer 2 is greater than buffer 1n"); 
   else 
      printf("buffer 2 is less than buffer 1n"); 
   ptr = strncmp(buf2,buf3,3); 
   if (ptr > 0) 
      printf("buffer 2 is greater than buffer 3n"); 
   else 
      printf("buffer 2 is less than buffer 3n"); 
   return(0); 
} 

函数名: strncmpi

功  能: 把串中的一部分与另一串中的一部分比较, 不管大小写

用  法: int strncmpi(char *str1, char *str2);

程序例: 

#include <string.h> 
#include <stdio.h> 
int main(void) 
{ 
   char *buf1 = "BBBccc", *buf2 = "bbbccc"; 
   int ptr; 
   ptr = strncmpi(buf2,buf1,3); 
   if (ptr > 0) 
      printf("buffer 2 is greater than buffer 1n"); 
   if (ptr < 0) 
      printf("buffer 2 is less than buffer 1n"); 
   if (ptr == 0) 
      printf("buffer 2 equals buffer 1n"); 
   return 0; 
} 

  

函数名: strncpy

功  能: 串拷贝

用  法: char *strncpy(char *destin, char *source, int maxlen);

程序例: 

#include <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char string[10]; 
   char *str1 = "abcdefghi"; 
   strncpy(string, str1, 3); 
   string[3] = ''; 
   printf("%sn", string); 
   return 0; 
} 

函数名: strnicmp

功  能: 不注重大小写地比较两个串

用  法: int strnicmp(char *str1, char *str2, unsigned maxlen);

程序例: 

#include <string.h> 
#include <stdio.h> 
int main(void) 
{ 
   char *buf1 = "BBBccc", *buf2 = "bbbccc"; 
   int ptr; 
   ptr = strnicmp(buf2, buf1, 3); 
   if (ptr > 0) 
      printf("buffer 2 is greater than buffer 1n"); 
   if (ptr < 0) 
      printf("buffer 2 is less than buffer 1n"); 
   if (ptr == 0) 
      printf("buffer 2 equals buffer 1n"); 
   return 0; 
} 

函数名: strnset

功  能: 将一个串中的所有字符都设为指定字符

用  法: char *strnset(char *str, char ch, unsigned n);

程序例:

#include <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char *string = "abcdefghijklmnopqrstuvwxyz"; 
   char letter = 'x'; 
   printf("string before strnset: %sn", string); 
   strnset(string, letter, 13); 
   printf("string after  strnset: %sn", string); 
   return 0; 
} 

函数名: strpbrk

功  能: 在串中查找给定字符集中的字符

用  法: char *strpbrk(char *str1, char *str2);

程序例: 

#include <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char *string1 = "abcdefghijklmnopqrstuvwxyz"; 
   char *string2 = "onm"; 
   char *ptr; 
   ptr = strpbrk(string1, string2); 
   if (ptr) 
      printf("strpbrk found first character: %cn", *ptr); 
   else 
      printf("strpbrk didn't find character in setn"); 
   return 0; 
} 

函数名: strrchr

功  能: 在串中查找指定字符的最后一个出现

用  法: char *strrchr(char *str, char c);

程序例: 

#include <string.h> 
#include <stdio.h> 
int main(void) 
{ 
   char string[15]; 
   char *ptr, c = 'r'; 
   strcpy(string, "This is a string"); 
   ptr = strrchr(string, c); 
   if (ptr) 
      printf("The character %c is at position: %dn", c, ptr-string); 
   else 
      printf("The character was not foundn"); 
   return 0; 
} 

  

函数名: strrev

功  能: 串倒转

用  法: char *strrev(char *str);

程序例: 

#include <string.h> 
#include <stdio.h> 
int main(void) 
{ 
   char *forward = "string"; 
   printf("Before strrev(): %sn", forward); 
   strrev(forward); 
   printf("After strrev():  %sn", forward); 
   return 0; 
} 

  

函数名: strset

功  能: 将一个串中的所有字符都设为指定字符

用  法: char *strset(char *str, char c);

程序例:

#include <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char string[10] = "123456789"; 
   char symbol = 'c'; 
   printf("Before strset(): %sn", string); 
   strset(string, symbol); 
   printf("After strset():  %sn", string); 
   return 0; 
} 

函数名: strspn

功  能: 在串中查找指定字符集的子集的第一次出现

用  法: int strspn(char *str1, char *str2);

程序例:

#include <stdio.h> 
#include <string.h> 
#include <alloc.h> 
int main(void) 
{ 
   char *string1 = "1234567890"; 
   char *string2 = "123DC8"; 
   int length; 
   length = strspn(string1, string2); 
   printf("Character where strings differ is at position %dn", length); 
   return 0; 
} 

函数名: strstr

功  能: 在串中查找指定字符串的第一次出现

用  法: char *strstr(char *str1, char *str2);

程序例:

#include <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char *str1 = "Borland International", *str2 = "nation", *ptr; 
   ptr = strstr(str1, str2); 
   printf("The substring is: %sn", ptr); 
   return 0; 
} 

函数名: strtod

功  能: 将字符串转换为double型值

用  法: double strtod(char *str, char **endptr);

程序例: 

#include <stdio.h> 
#include <stdlib.h> 
int main(void) 
{ 
   char input[80], *endptr; 
   double value; 
   printf("Enter a floating point number:"); 
   gets(input); 
   value = strtod(input, &endptr); 
   printf("The string is %s the number is %lfn", input, value); 
   return 0; 
}

函数名: strtok

功  能: 查找由在第二个串中指定的分界符分隔开的单词

用  法: char *strtok(char *str1, char *str2);

程序例:

#include <string.h> 
#include <stdio.h> 
int main(void) 
{ 
   char input[16] = "abc,d"; 
   char *p; 
   /* strtok places a NULL terminator 
   in front of the token, if found */ 
   p = strtok(input, ","); 
   if (p)   printf("%sn", p); 
   /* A second call to strtok using a NULL 
   as the first parameter returns a pointer 
   to the character following the token  */ 
   p = strtok(NULL, ","); 
   if (p)   printf("%sn", p); 
   return 0; 
} 

函数名: strtol

功  能: 将串转换为长整数

用  法: long strtol(char *str, char **endptr, int base);

程序例: 

#include <stdlib.h> 
#include <stdio.h> 
int main(void) 
{ 
   char *string = "87654321", *endptr; 
   long lnumber; 
   /* strtol converts string to long integer  */ 
   lnumber = strtol(string, &endptr, 10); 
   printf("string = %s  long = %ldn", string, lnumber); 
   return 0; 
} 

函数名: strupr

功  能: 将串中的小写字母转换为大写字母

用  法: char *strupr(char *str);

程序例:

#include <stdio.h> 
#include <string.h> 
int main(void) 
{ 
   char *string = "abcdefghijklmnopqrstuvwxyz", *ptr; 
   /* converts string to upper case characters */ 
   ptr = strupr(string); 
   printf("%sn", ptr); 
   return 0; 
} 

函数名: swab

功  能: 交换字节

用  法: void swab (char *from, char *to, int nbytes);

程序例:

#include <stdlib.h> 
#include <stdio.h> 
#include <string.h> 
char source[15] = "rFna koBlrna d"; 
char target[15]; 
int main(void) 
{ 
   swab(source, target, strlen(source)); 
   printf("This is target: %sn", target); 
   return 0; 
}